1. Field of the Invention
The present invention relates to a semiconductor device, particularly to a chip-size packaged resin-sealed type semiconductor device. Moreover, the present invention also relates to a method of manufacturing such semiconductor device.
1. Background Information
In recent years, as portable devices typified by notebook PCs and cellular phones become rapidly popular, semiconductor devices to be mounted on such portable devices must become smaller, thinner and lighter. One key technology which realizes such needs is a high-density packaging technique, such as a CSP (chip size package) which is extremely close to the size of a semiconductor chip. Particularly, a W-CSP (Wafer Level Chip Size Package) technique, in which the sealing process is done in a wafer state, is considered to be an ultimate compact package, and it is drawing increasing attention because may provide advantages such as reduction in manufacturing costs.
A conventional semiconductor device manufactured by using the W-CSP technique has wirings connected to each of the electrode pads of a semiconductor chip, conductive posts connected to the wirings, a sealing resin covering the semiconductor chip at about the same level as the layer of the conductive posts, and external electrodes formed at the end of each of the conductive posts. In this connection, there is a LGA type, a BGA type, or the like, depending on the shape of the external electrode.
One example of a chip-size package type semiconductor device is shown in Japanese Laid-Open Patent Application No. 2000-22699 (hereinafter to be referred to as Patent Reference 1). The semiconductor device of Patent Reference 1 has wirings made of a copper material formed on a semiconductor substrate, columnar electrodes (i.e., conductive posts) made of a copper material formed on the wirings, and a sealing resin formed on the semiconductor substrate and the wirings, in a way that covers the lateral surfaces of the columnar electrodes. Copper oxide films are formed on the surfaces of the wirings and the lateral surfaces of the columnar electrodes.
In a conventional semiconductor device manufactured by using a typical W-CSP technique, a structure is adopted in which the sealing resin is directly adhered to the lateral surfaces of the conductive posts. However, the adhesiveness between the sealing resin and the conductive posts is not necessarily sufficient. When the adhesiveness between the sealing resin and the conductive posts becomes weak due to manufacturing error etc., the sealing resin may become easily separated from the lateral surfaces of the conductive posts, which results in the generation of gaps between the sealing resin and the conductive posts. When gaps are generated between the sealing resin and the conductive posts, there is a possibility, for instance, that moisture will enter inside the package through the gaps, which may result in the occurrence of corrosion on the elements made of a metal material, such as the conductive posts and the wirings. As for other possible problems which may be caused by having gaps between the sealing resin and the conductive posts, for instance, the conductive posts may be displaced due to external force, which may result in the generation of cracks in the insulation film etc. on the surface of the semiconductor chip.
Considering such possible problems, the semiconductor device disclosed in Patent Reference 1 has adhesive layers made of copper oxide formed on the lateral surfaces of the columnar electrodes (i.e., the conductive posts) in order to strengthen the adhesiveness between the sealing resin and the columnar electrodes, and make the sealing resin difficult to break away. However, forming a copper oxide film on the lateral surfaces of the columnar electrodes requires a large number of processes, such as a wet-etching process for making the surfaces of the columnar electrodes pure copper surfaces, a pre-baking process for making the substrate temperature uniform at a predetermined temperature, a main baking process for oxidizing the surfaces of the columnar electrodes in order to form the copper oxide film, and so forth. Such increase in the number of processes inevitably leads to an increase in production costs.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved semiconductor device and an improved method of manufacturing a semiconductor device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.